Failure to Launch fails at more than just launching. It fails at romance and comedy. It fails to make the lead characters interesting and their love affair believable. And it fails to develop a consistent tone that would enable viewers to suspend their disbelief and be carried away by a simple tale of two people falling for each other. It's difficult to say whether the leads are miscast or whether the parts are badly written (likely a combination of both), but the pairing of Sarah Jessica Parker and Matthew McConaughey generates as many sparks as a soaked match in a rainstorm. Not only are these two unromantic, but their characters are self-absorbed and dull. So it's left to the supporting characters to provide Failure to Launch's few, occasional pleasures.

What does it mean when one of the highlights of a movie is a shot of Terry Bradshaw's naked butt? No offense to the ex-quarterback's sagging cheeks, but that's a bad sign. (Bradshaw's on-screen spouse, Kathy Bates, got guffaws - and groans - when she bared all in About Schmidt. The difference is that About Schmidt had a lot more going for it than Failure to Launch.) Other positives are hard to unearth. I liked the Zooey Deschanel character and subplot until her boyfriend gave mouth-to-beak resuscitation to a downed bird. That scene - as well as a few others - belongs in different movie. As a filmmaker, why undermine the tenuous "reality" of your characters by reducing them to pawns in cartoonish sequences that would be more appropriate in a Saturday Night Live skit?

The lovers in this story are Trip (McConaughey) and Paula (Sarah Jessica Parker). He's a layabout who, at age 35, lives with his parents, expects his mother to cook and clean for him, and uses his living arrangements to get him out of relationships that become serious. She's an "interventionist" - someone Trip's Mom (Kathy Bates) and Dad (Terry Bradshaw) hire to get their son to move out. The plan is simple: Paula will get Trip to fall for her, which will lead to him wanting to assert his independence. Complications ensue. Trip isn't willing to give up his cozy lifestyle. Paula falls for her client and violates her "no sex" rule. And Trip's friend, Ace (Justin Bartha), finds out about the scheme. To keep him quiet, Paula offers a date with her ill-tempered roommate, Kit (Zooey Deschanel), who has never read Harper Lee but still wants to kill a mockingbird.

It puzzles me why a director would assume all that's necessary for a romantic comedy to work is that two recognizable stars be paired together. Chemistry is the single biggest factor in the success of this sort of film. When the actors don't have it, as in Failure to Launch, the film is doomed. There are some funny moments during the production (although not enough) and some of the supporting characters are worthy of notice, but nothing can detract from the gaping hole that exists where the romance is supposed to be. Even the big "true confessions" scene comes across as false and contrived. Admittedly, irrespective of the movie, this obligatory scene is almost always false and contrived, but if we believe in the romance, we accept it. Failure to Launch doesn't get us close to that point.

The tone is uneven. Director Tom Dey drags us on a bumper car ride from over-the-top, cartoonish comedy to cheesy melodrama, with a variety of stops in between. One of the few bright spots is Zooey Deschanel. 30 minutes into the film, I realized I wanted the movie to be about Kit, but that's not what the director had in mind. Nevertheless, the character's prominence is inexplicable until one looks at the running time. If Failure to Launch relied solely on its main plot, it would have clocked in at about 60 minutes. So Kit's mockingbird/reluctant romance is necessary to pad things out. Another positive is (surprisingly) Terry Bradshaw, who is genuinely funny - although every moment of screen time is designed to build to the buttocks shot.

The romantic comedy rules are simple. Filmmakers who follow them may not generate timeless classics, but they provide audiences with fantasies that can be savored in the short term. Those who ignore the rules or can't figure out how to make them work are doomed to produce inept and unwieldy pictures that will frustrate viewers by providing glimpses of the fantasy without delivering it. Such is the case with Failure to Launch. Different leads might not have solved all the problems, but that move would have represented a step in the right direction. McConaughey and Parker may be popular and charismatic, but they look like they would rather be anywhere else except in each other's arms.